Trouble exporting in correct file format
Blender will never generate text files for images, it cannot do that. This is a user error and improper configuration in blender or the OS

What might be happening is that the option to add the proper extension to the file name has been disabled and the OS does not know what kind of file it is dealing with. If you are using windows the computer cannot guess what to do with files that do not have the 3 letter extension at the end of the file name (like *.jpg)

Options to fix the issue: on the already rendered images just add the proper extension to the file for exmaple: image01.jpg (if the image is a jpg file).

For future renders enable the File extensions box on the output settings.



If your OS is still trying to open files with the .jpg extension as text, then you need to configure it to use a different deafult app. In which case it is not an issue with blender and will require you to learn how to use your computer and set the default app to open image files.